For transmission line structures, propagation delay corresponds to the amount of time required for a signal to propagate its length. Manufactures of computers, integrated circuits, memories and other electrical circuits continually strive to reduce propagation delays in order to improve system operating speeds.
In the past, manufactures have been working to reduce circuit geometries, which has had the effect of improving operating speeds by way of reduced line lengths. More recently, however, manufactures are looking for additional means to improve operating speed. Such measures have included, e.g., lowering the resistance of conductive lines to reduce their RC delays.
In short, there have been continued efforts to provide computers, CPU""s, semiconductor memories, integrated circuits, circuit boards, buses and other electrical devices structures and circuits to propagate signals quickly.